k8s: Use Kubernetes DNS instead of service env vars.

This removes the restriction that all services used by a pod must
already have been created before the pod is created. It also allows a
service to be deleted and recreated without having to also recreate all
pods that depend on that service.

examples/kubernetes/etcd-controller-template.yaml

@@ -45,16 +45,9 @@ spec:
             - >-
               ipaddr=$(hostname -i)
 
-              global_etcd=$ETCD_GLOBAL_SERVICE_HOST:$ETCD_GLOBAL_SERVICE_PORT
-
-              cell="{{cell}}" &&
-              local_etcd_host_var="ETCD_${cell^^}_SERVICE_HOST" &&
-              local_etcd_port_var="ETCD_${cell^^}_SERVICE_PORT" &&
-              local_etcd=${!local_etcd_host_var}:${!local_etcd_port_var}
-
               if [ "{{cell}}" != "global" ]; then
-              until etcdctl -C "http://$global_etcd"
-              set "/vt/cells/{{cell}}" "http://$local_etcd"; do
+              until etcdctl -C "http://etcd-global:4001"
+              set "/vt/cells/{{cell}}" "http://etcd-{{cell}}:4001"; do
               echo "[$(date)] waiting for global etcd to register cell '{{cell}}'";
               sleep 1;
               done;

examples/kubernetes/guestbook/main.py

@@ -98,8 +98,8 @@ def env():
 if __name__ == "__main__":
   timeout = 10 # connect timeout in seconds
 
-  # Get vtgate service address from Kubernetes environment.
-  addr = '%s:%s' % (os.environ['VTGATE_SERVICE_HOST'], os.environ['VTGATE_SERVICE_PORT'])
+  # Get vtgate service address from Kubernetes DNS.
+  addr = 'vtgate:15001'
 
   # Connect to vtgate.
   conn = vtgatev2.connect({'vt': [addr]}, timeout)

examples/kubernetes/vtctld-controller-template.yaml

@@ -51,7 +51,7 @@ spec:
               -topo_implementation etcd
               -tablet_protocol grpc
               -tablet_manager_protocol grpc
-              -etcd_global_addrs http://$ETCD_GLOBAL_SERVICE_HOST:$ETCD_GLOBAL_SERVICE_PORT
+              -etcd_global_addrs http://etcd-global:4001
               {{backup_flags}}" vitess
       volumes:
         - name: syslog

examples/kubernetes/vtgate-controller-benchmarking-template.yaml

@@ -30,7 +30,7 @@ spec:
               chown -R vitess /vt &&
               su -p -c "/vt/bin/vtgate
               -topo_implementation etcd
-              -etcd_global_addrs http://$ETCD_GLOBAL_SERVICE_HOST:$ETCD_GLOBAL_SERVICE_PORT
+              -etcd_global_addrs http://etcd-global:4001
               -log_dir $VTDATAROOT/tmp
               -alsologtostderr
               -port 15001

examples/kubernetes/vtgate-controller-template.yaml

@@ -36,7 +36,7 @@ spec:
               chown -R vitess /vt &&
               su -p -c "/vt/bin/vtgate
               -topo_implementation etcd
-              -etcd_global_addrs http://$ETCD_GLOBAL_SERVICE_HOST:$ETCD_GLOBAL_SERVICE_PORT
+              -etcd_global_addrs http://etcd-global:4001
               -log_dir $VTDATAROOT/tmp
               -alsologtostderr
               -port 15001

examples/kubernetes/vttablet-pod-benchmarking-template.yaml

@@ -43,7 +43,7 @@ spec:
 
           su -p -s /bin/bash -c "/vt/bin/vttablet
           -topo_implementation etcd
-          -etcd_global_addrs http://$ETCD_GLOBAL_SERVICE_HOST:$ETCD_GLOBAL_SERVICE_PORT
+          -etcd_global_addrs http://etcd-global:4001
           -log_dir $VTDATAROOT/tmp
           -alsologtostderr
           -port {{port}}

examples/kubernetes/vttablet-pod-template.yaml

@@ -44,7 +44,7 @@ spec:
 
           su -p -s /bin/bash -c "/vt/bin/vttablet
           -topo_implementation etcd
-          -etcd_global_addrs http://$ETCD_GLOBAL_SERVICE_HOST:$ETCD_GLOBAL_SERVICE_PORT
+          -etcd_global_addrs http://etcd-global:4001
           -log_dir $VTDATAROOT/tmp
           -alsologtostderr
           -port {{port}}

examples/kubernetes/vtworker-pod-template.yaml

@@ -25,7 +25,7 @@ spec:
           -alsologtostderr
           -port {{port}}
           -topo_implementation etcd
-          -etcd_global_addrs http://$ETCD_GLOBAL_SERVICE_HOST:$ETCD_GLOBAL_SERVICE_PORT
+          -etcd_global_addrs http://etcd-global:4001
           -min_healthy_rdonly_endpoints 1
           -cell {{cell}}
           -tablet_protocol grpc